1. Field of the Invention
This invention relates to pump impellers and specifically relates to an impeller having vanes particularly configured to selectively determine the velocity profile of the impeller to thereby selectively modify the wear of the pump casing when processing slurries.
2. Description of Related Art
Rotodynamic pumps are used in a variety of industries to process liquids and slurries. The type of fluid being processed dictates the type and configuration of the pump that is used in the particular application. That is, pumping clear liquid places less demand on pumps than does the processing of slurries, which contain an amount of solids or particulate matter that is abrasive and degrading to the internal structures of the pump.
Therefore, pump designers and engineers must consider the type of fluid or slurry that is going to be processed and select or design an impeller and pump casing that is most suitable to the application. For example, in the processing of clear liquids (e.g., water), it is typical that the pump casing is a volute, the shape of which changes in cross sectional area from the cutwater of the pump to near the outlet of the pump, and comparatively little wear is observed in the pump casing.
In the processing of slurries however, pump designers must consider the effect of hydraulic surface geometry not only from the point of optimizing pump efficiency, but also from the standpoint of minimizing wear in the pump casing. Thus, it has been typical in slurry pump design to modify the general volute shape of clear liquid-processing pumps to provide, for example, wider impeller outlets and casings with parallel sides.
Another factor that determines wear on the pump casing is the shape of the impeller vanes. Specifically, the outer edge of the vanes of the impeller have been demonstrated to significantly effect the flow velocity of fluid moving through the pump. It has been observed that the typical vane configuration having a straight outer edge, at or near the periphery of the shroud, produces a certain fluid velocity that leads to wear on the pump casing along the sides of the volute.
Thus, it would be advantageous in the art to provide an impeller having vanes that are specifically designed or configured to produce a more even wear pattern thus extending the overall wear life of the pump casing when processing slurries, particularly those with high solids content and/or particularly abrasive solids content.